This invention relates generally to an ink jet printing head of the type used to project drops of ink on a printing media for printing and more particularly to an ink jet printing head using a piezoelectric element to change the volume of a pressure chamber so as to eject an ink drop from a nozzle. Many methods to provide an ink-on-demand type ink jet printer had been proposed in the prior art but these generally present large resistance to flow within the fluid channels and thus need a long period of time to make up for ejected ink. Also many of these printer head designs require critical dimensioning of flow passages and there is difficulty in purging vapors from the flow passages once they have entered or formed in the printing head.
What is needed is an ink jet printing head which supplies ink on demand, is readily purged of internal vapors which may accumulate, has a short refill time, and is of simple construction.